The invention relates to a method of preparing starch graft copolymers and to the starch graft polymer composition prepared thereby. It further relates to starch graft copolymer reinforced solid and foamed rubber products and to their method of preparation.
Starch graft copolymers have been prepared by many methods, most of which involve the initiation of free radicals on the starch backbone molecule and the subsequent polymerization of a monomeric compound thereon (Block and Graft Copolymerization, Vol. 1, R. J. Ceresa, ed., John Wiley and Sons, 1973, Chapters 1 and 2). Other methods are ionic in reaction mechanics and include the reaction of a monomer with a starch containing a suitable functional group (usually an alkali metal alkoxide derivative of starch is used) and the reaction of a preformed reactive polymeric material with a suitable functional group derivative of starch. An example of this last method and its usefulness lies in our recent disclosures on the reaction of polyethyleneimine (PEI) with starch xanthate (SX) [Maher et al., Staerke 19: 354 (1967)]. The coprecipitation of the PEI and SX combination with rubber latices resulted in a solid rubber product having enhanced physical properties [Douglas et al., J. Appl. Polym. Sci. 16: 1937 (1972) ].